How old are the batteries? Have they been consistently charged to 14.4 to 14.6 volts? I believe the lead-acid batteries may have lost some capacity and while not dead they cannot hold the voltage up.
Otherwise I recommend 600+ Ah of lithium battery as a replacement if expecting to run the A/C for any length of time.
Brand new batteries. Two sets of deep cycle 6V golf cart batteries wired in series, then the 2 sets in parallel, 215 amp hours per battery. The solar charge controller is set to stop charging at 13.8V, perhaps I should set that higher? Was trying to avoid adding 2 more batteries, but that might be necessary...
Yes most GC2 will call for a couple hours absorption time at 14.4 - 14.8 volts. Verify with the manufacturer.
